The former Liverpool playmaker, a central figure in Spain's World Cup triumph in South Africa last year, picked up his fifth yellow card last weekend, though it does clear him to return for the pivotal clash against Barcelona at the Bernabeu the following Saturday.
Jose Mourinho's team have been in imperious form, racking up 13 consecutive victories in all competitions, and have pulled three points clear of their arch-rivals Barca, who have played a game more.
In Gijon, however, they will miss Alonso's influence in a hostile and intimidating environment.
Sporting, who are 18th, boast a noisy and colorful support who will not have forgotten last season's barbed exchanges between their popular and pugnacious coach Manuel Preciado and Mourinho.
Alonso brings composure and experience to Real's relatively young team and has been an important part of their resurgence.
The player brought in over the summer to help cover for his absences, Turkey's Nuri Sahin, has only just made his debut after an injury-delayed start to his career in Spain and is still finding his feet.
"We have taken a step forward this season. We are in a fantastic run of form and results, and we don't want it to stop," Alonso told reporters this week.
"I don't know if I am in the best form of my career, we'll wait and see how things turn out. The season is very long and we will have many high points and the odd setback, but hopefully not too many."
Real want all three points to keep the pressure on Barca, who are chasing their fourth consecutive league crown, and to maintain the psychological edge in the run up to next weekend's 'clasico'.
